MEASURE PREVIOUSLY BELIEVED TO BE RELIABLE INDICATOR OF SEVERITY OF EXERCISE-INDUCED ASTHMA IN CHILDREN PROVES OTHERWISE

 The severity of exercise-induced asthma in children cannot be determined by PCO₂ at the end of exercise. The results of a research study conducted in Australia will be presented at the 2000 Intersociety Meeting of the American Physiological Society in Portland, ME

 
Portland, ME— Asthma occurs when the bronchial airways contract, leading to  wheezing and difficulty in breathing.  Approximately l7 million Americans suffer from asthma and about 5,000 Americans die from the disease annually. Asthma is caused by an allergic reaction to pollens, animal dander, smoke, pollutants and other substances. It can also prompted by exercise.

Background: Exercise-induced asthma (EIA) is characterized by a narrowing of the airway, which typically occurs following exercise. In previous studies, high levels of CO₂ were observed in the expired air near the end of exercise (end tidal CO₂) in children with EIA.  This was taken to suggest that the airways were narrowing during exercise and preventing CO₂ from being removed from the lungs. A study conducted in Australia by R.G.D. Roberts, Ph.D., of the Royal Children's Hospital Department of Respiratory Medicine, indicates that end tidal CO₂ is not a reliable indicator of the severity of EIA in children. Dr. Roberts will discuss his research findings at the intersociety meeting of the American Physiological Society. The meeting, "The Integrative Biology of Exercise," will be held September 20-23, 2000 in Portland, ME.

Methodology: To determine whether the severity of EIA can be predicted by breathing responses near the end of exercise, Dr. Roberts and his colleagues studied 78 children with doctor-diagnosed asthma and no preventive pre-medication. The children completed an 8-minute incremental treadmill walk/run to 60 percent of their estimated maximum ventilatory capacity, while breathing dry air. The EIA was assessed by the percent fall in lung function (FEV1) during the 15 minutes following exercise.

Results: The results of the study demonstrated in those children – totaling 43 -- with a significant airway narrowing response to exercise, that there was no correlation between the degree of airway narrowing and end tidal CO₂ near the end of exercise. 

Conclusion: This suggests that the response of each child with EIA to exercise is highly individual.  To make a reliable assessment of the severity of EIA it is better to focus on measurements of post exercise lung function than on changes in physiological variables during exercise.

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Editor's Note: For further information or to schedule an interview, contact Donna Krupa at 703.527.7357; cell: 703.967.2751; or at djkrupa1@aol.com; or visit the APS website at www.the-aps.org.